This invention relates generally to hand-held pneumatic rotary drive devices, and more particularly to a device of this class for driving a grinding wheel, useful as a die grinder.
Reference may be made to U.S. Pat. No. 5,535,646 issued Jul. 16, 1996 showing in FIG. 9 thereof a hand-held pneumatic rotary drive device generally of the same class as the present invention, albeit for use with a bidirectional ratchet drive for a tool.
Hand-held pneumatic rotary drive devices of the type with which this invention is concerned have a pneumatic motor for effecting driving of the instrumentality to be driven thereby, supplied with compressed air via an air hose. Flexibility of the hose permits the manipulation of the device by hand to do the work intended. This invention is especially concerned with the pneumatic circuitry involved, and more particularly with problems which have been encountered in the exhausting of air from prior devices, such as the problem of exhaust air blowing in the user's eyes (often with particles of debris in the air), exhaust air blowing up the user's sleeve, and the problem of excessive noise.